1. Technical Field
The present disclosure relates to a vehicle control device and a vehicle control method.
2. Related Art
Conventionally, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2012-029473 describes that a slip of drive wheels is determined on the basis of a comparison of a value corresponding to estimated motor rotation speed with a value corresponding to the actual motor rotation speed, the estimated motor rotation speed being estimated by using a transmission characteristic between motor torque and motor rotation speed based on the torsional rigidity of a drive system.
It is desirable to suppress, in as short a time as possible, a slip of drive wheels, which occurs when a vehicle begins to move or travels at very slow speed. It is, however, difficult to suppress a slip when drive units such as motors are configured to be connected with respective tires (wheels) via drive shafts because feedback control over the drive units based on the tire rotation speed obtained from a sensor increases time delay in detection owing to the separation of the tires from the drive units, and the tire rotation speed increases during this time delay.
Meanwhile, feedback control over the drive units based on the rotation speed of the drive units obtained from a sensor can certainly decrease time delay, but torsional vibration of the drive shafts may unfortunately degrade controllability because the drive shafts are installed between the drive units and the tires.
The technology described in JP-A No. 2012-029473 determines a slip of drive wheels, on the basis of a comparison of a value corresponding to estimated motor rotation speed with a value corresponding to the actual motor rotation speed, the estimated motor rotation speed being based on the torsional rigidity of a drive system. However, control based on tire rotation speed after a slip determination increases tire rotation speed during time delay as mentioned above, so that it is difficult to suppress a slip. If control based on motor rotation speed continues after a slip determination, torsional vibration of drive shafts as mentioned above unfortunately degrades controllability.